Semiconductor wafers such as silicon and gallium arsenide wafers are manufactured in a large diameter state, and the wafers are cut and separated (diced) into small element pieces (semiconductor chips), which are then transferred to a mounting step as the subsequent step. During this operation, semiconductor wafers are subjected to the steps of dicing, cleaning, drying, expanding, and pickup in a state of being preliminarily attached to adhesive sheets, and these steps are followed by a bonding step as the subsequent step.
To simplify the processes of the pickup step and bonding step among the above steps, there have been proposed various adhesive sheets for dicing/die bonding that have both of a wafer fixing function and a die adhesion function (Patent Literature 1, etc). The adhesive sheet as disclosed in Patent Literature 1 allows so-called direct die bonding and can omit a coating step for adhesive for die adhesion. Such an adhesive sheet may be formed by laminating a die-bonding layer formation film comprising an adhesive layer formed of a specific composition on a pressure sensitive adhesive layer of a pressure sensitive adhesive sheet comprising the pressure sensitive adhesive layer and a base film.
In recent years, based on the fact that a semiconductor device has been manufactured in which a plurality of semiconductor chips are laminated in multiple layers, there is needed a die-bonding layer formation film in which bubbles (voids) are less likely to grow at the boundary with an adherend even when heated. It is expected that a die-bonding layer that is unlikely to delaminate from an adherend can be formed from such a die-bonding layer formation film.
In this regard, Patent Literature 2 discloses a thermosetting-type die-bonding film (die-bonding layer formation film) that is used for fixing a semiconductor chip to an adherend and has at least an adhesive layer. The thermosetting-type die-bonding film has the following features. The adhesive layer contains an epoxy resin and phenol resin as thermoset resins and also contains an acrylic resin having a weight-average molecular weight of 100,000 or more as a thermoplastic resin. When the total weight of the epoxy resin and phenol resin is X and the weight of the acrylic resin is Y, the value X/Y ranges from 0.07 to 0.7. After heating treatment at 175° C. for 1 hour, the decrease ratio of epoxy groups in terms of that before the heating treatment is 60% or less. It is said that the adhesive layer of the die-bonding layer formation film disclosed in Patent Literature 2 can suppress the progress of thermoset reaction at the time of heating and the progress of cross-linking thereby to allow voids to readily disappear due to the heat and pressure during molding even when such voids are generated at the boundary between the adhesive layer and an adherend. In the present description, an “adhesive layer excellent in thermal history resistance” refers to an adhesive layer that allows bubbles (voids) to readily disappear before a die-bonding layer is formed, even when the die-bonding layer formation film receives thermal history, such as heating at 175° C. for 1 hour, to generate bubbles (voids) at the boundary between the adhesive layer of the die-bonding layer formation film and an adherend.